Using sacrificial solids in semiconductor processing

ABSTRACT

In an example, a method may include closing an opening in a structure with a sacrificial material at a first processing tool, moving the structure from the first processing tool to a second processing tool while the opening is closed, and removing the sacrificial material at the second processing tool. The structure may be used in semiconductor devices, such as memory devices.

TECHNICAL FIELD

The present disclosure relates generally to semiconductor processing,and, more particularly, to using sacrificial solids in semiconductorprocessing.

BACKGROUND

Semiconductor processing (e.g., fabrication) can be used to formsemiconductor devices, such as integrated circuits, memory devices,microelectromechanical devices (MEMS), etc.

Examples of memory devices that can be formed by semiconductorprocessing include, but are not limited to, volatile memory (e.g., thatcan require power to maintain its data), such as random-access memory(RAM), dynamic random access memory (DRAM), synchronous dynamic randomaccess memory (SDRAM), among others, and non-volatile memory (e.g., thatcan provide persistent data by retaining stored data when not powered),such as NAND flash memory, NOR flash memory, read only memory (ROM),electrically erasable programmable ROM (EEPROM), erasable programmableROM (EPROM, among others.

Semiconductor processing can involve forming features (e.g., patterns)on and/or in a semiconductor (e.g., of silicon) that may be referred toas a wafer or substrate. In some examples, one or more materials, suchas silicon-based materials (e.g., silicon oxide (SiO), silicon nitride(SiN), tetraethyl orthosilicate (TEOS), and/or polysilicon) may beformed on the semiconductor. For instance, a deposition process, such asphysical vapor deposition (PVD), chemical vapor deposition (CVD), atomiclayer deposition (ALD), electrochemical deposition and/or molecular beamepitaxy, among others may be used to form one or more materials on thesemiconductor.

Subsequently, portions of the one or more materials, and in someinstances, portions of the semiconductor, may be removed, such as by wetand/or dry etching, to form the features. In some examples, the featuresmay have high aspect ratios (e.g., ratio of height to width or diameter)and may be referred to as high-aspect-ratio (HAR) features. For example,the features might be separated from each other by HAR openings.

During processing, the semiconductor and the features may be subjectedto wet processing, such as wet cleaning, and subsequent drying. Forexample, wet cleaning can be helpful to remove residue left behind, suchas by the removal process or other processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents various examples of feature toppling.

FIGS. 2A-2F illustrate cross-sectional views of processing stepsassociated with forming a semiconductor device, in accordance with anumber of embodiments of the present disclosure.

FIG. 3 an example of a processing step associated with forming asemiconductor device, in accordance with a number of embodiments of thepresent disclosure.

FIG. 4 is a block diagram illustration of a processing apparatus used inconjunction with the processing steps associated with forming asemiconductor device, in accordance with a number of embodiments of thepresent disclosure.

FIG. 5 is a block diagram illustration of an apparatus formed, at leastin part, in accordance with a number of embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure includes processing methods associated withforming semiconductor devices, such as integrated circuits, memorydevices MEMS, among others. A number of embodiments include methods offorming semiconductor devices, comprising: closing an opening in astructure with a solid sacrificial material at a first processing tool,moving the structure from the first processing tool to a secondprocessing tool while the opening is closed, and removing thesacrificial material at the second processing tool. The structure may beused in semiconductor devices, such as integrated circuits, memorydevices, MEMS, among others.

Embodiments of the present disclosure provide technical advantages, suchas reducing the likelihood of feature collapse (e.g. toppling) duringprocessing compared to previous approaches. For instance, a number ofembodiments form a sacrificial material in openings between features ina structure, such as a structure to be used in a semiconductor device(e.g., a memory device), that acts to prevent feature collapse (e.g.,sometimes referred to as pattern collapse) while the structure is beingmoved from one processing tool to another processing tool duringprocessing (e.g., formation of the semiconductor device).

Some prior approaches can include forming features in a structure at adry etch tool, such as by dry etching, and moving the structure to a wetcleaning tool (e.g., to clean residue from the dry etch from thestructure). After cleaning, the structure may be moved to a depositiontool that may add additional material to the structure. However, thestructures may be exposed to moisture-containing air as they are beingmoved from tool to tool.

For instance, water vapor from the air can condense on surfaces ofstructures (e.g., forming liquid condensate) as they are being moved.This can be a problem for structures having small openings betweenfeatures, such as HAR features. For example, the liquid condensate mayform in the openings between the features. High surface tension forcesmay result from the liquid in the openings that can cause the featuresto topple (e.g., collapse) toward each other, bringing adjacent featuresinto contact with each other. For example, FIG. 1 illustrates a feature101 toppling (e.g., collapsing) into an adjacent feature and a pair ofadjacent features 102 toppling into each other (e.g. in what issometimes referred to as bridging). This can lead to defects in thesemiconductor device structure, and can even render the semiconductordevice inoperable.

The sacrificial materials of the embodiments described herein close theopenings to prevent liquid condensate from forming in the openings whilethe structures are being moved from tool to tool, and thus can reducethe likelihood of (e.g., eliminate) toppling.

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown, byway of illustration, specific examples. In the drawings, like numeralsdescribe substantially similar components throughout the several views.Other examples may be utilized and structural and electrical changes maybe made without departing from the scope of the present disclosure. Thefollowing detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present disclosure is defined onlyby the appended claims and equivalents thereof.

The term semiconductor can refer to, for example, a layer of material, awafer, or a substrate, and includes any base semiconductor structure.“Semiconductor” is to be understood as including silicon-on-sapphire(SOS) technology, silicon-on-insulator (SOI) technology,thin-film-transistor (TFT) technology, doped and undoped semiconductors,epitaxial layers of a silicon supported by a base semiconductorstructure, as well as other semiconductor structures. Furthermore, whenreference is made to a semiconductor in the following description,previous process steps may have been utilized to form regions/junctionsin the base semiconductor structure, and the term semiconductor caninclude the underlying layers containing such regions/junctions.

The figures herein follow a numbering convention in which the firstdigit or digits correspond to the drawing figure number and theremaining digits identify an element or component in the drawing.Similar elements or components between different figures may beidentified by the use of similar digits. For example, 211 may referenceelement “11” in FIG. 2A, and a similar element may be referenced as 311in FIG. 3. As will be appreciated, elements shown in the variousembodiments herein can be added, exchanged, and/or eliminated so as toprovide a number of additional embodiments of the present disclosure. Inaddition, as will be appreciated, the proportion and the relative scaleof the elements provided in the figures are intended to illustrate theembodiments of the present disclosure, and should not be taken in alimiting sense.

FIGS. 2A-2F illustrate cross-sectional views of processing stepsassociated with forming a semiconductor device, such as a portion of anintegrated circuit, a memory device, a MEMS, among others, in accordancewith a number of embodiments of the present disclosure. For example, theprocessing steps may be associated with forming (e.g., a memory arrayof) a DRAM memory device, a NAND flash memory device, a NOR flash memorydevice, among others.

FIG. 2A depicts a structure (e.g., to be used in a semiconductor device)after several processing steps have occurred. The structure may includea base structure, such as a substrate 206 (e.g., a semiconductor). Insome examples, one or more materials 210, such as silicon-basedmaterials, may be formed on (e.g., over) a surface 208, such as an uppersurface, of semiconductor 206, using, for example, a deposition process,such as PVD, CVD, ALD, electrochemical deposition and/or molecular beamepitaxy, among others.

Features 211, such as nanofeatures (e.g., having a width or diameter ofabout 0.1 nanometer to about 100 nanometer) are formed by removingportions of the structure, such as portions of the one or more materials210 and portions of semiconductor 206. The removal process formsopenings 212, such as spaces (e.g., trenches), through the one or morematerials 210, stopping on or in (e.g., as shown in FIG. 2A)semiconductor 206. For example, an opening 212 may be between adjacentfeatures 211. In some examples, each of the respective features 211includes the one or more materials 210 and a portion of semiconductor206.

In some examples, portions of the openings 212 in semiconductor 206(e.g., below surface 208) may correspond to isolation regions, such asshallow trench isolation (STI) regions. In an example, a feature 211 maybe entirely of semiconductor 206, and openings 212 may correspond to STIregions. Features 211 may be HAR features, and openings 212 may be HARopenings. For example, a HAR may have a height to width or diameterratio of 10 to 1, 25 to 1, or greater.

In some examples, openings 212, and thus the structure in FIG. 2A, maybe formed using a dry processing tool, such as the dry removal tool 435(e.g., dry etch tool) of the processing (e.g., semiconductor processing)apparatus 433 in FIG. 4, using a dry removal process, such as a dryetch. A mask (not shown), such as imaging resist (e.g., photo-resist),may be formed over the one or more materials 210 and patterned to exposeregions of the one or more materials 210. The exposed regions may besubsequently removed, such as by the dry etch process, to form openings212 that may terminate on or in semiconductor 206.

As shown in FIG. 2B, a sacrificial material 214, such as a dielectricmaterial (e.g., silicon oxide, silicon nitride, etc.), an organiccompound (e.g., an organic polymer), an ionic compound (e.g., anammonium salt or a halide salt), a soluble material (e.g., soluble in asolvent, such as water, hydrofluoric acid (HF), etc.) among others, isformed on the structure of FIG. 2A to close openings 212. For example,ammonium salt and halide salt are water soluble and oxalic acid,acetamide, and urea are organic compounds that are soluble in water andorganic solvents. In other examples, sacrificial material 214 mayinclude semiconductors, such as silicon (e.g., for cases when thestructure is of a material different that silicon, germanium, amongothers, or a conductor, such as a metal (e.g., tungsten, aluminum,titanium, titanium nitride, etc.), among others. In some examples,sacrificial material 214 can completely fill openings 212 such that anupper surface of sacrificial material 214 may be coplanar (e.g., flush)with the upper surfaces 216 of features 211. Additionally, as shown inFIG. 2B, sacrificial material 214 can overfill openings 212 and extendover (e.g., cover) upper surfaces 216 of features 211.

The sacrificial material 214 may be formed on the structure of FIG. 2Aat dry removal tool 435, such as in the same processing chamber in whichthe dry etch is performed, before the resulting structure in FIG. 2B isexposed to a moisture-containing atmosphere, such as air. For example,sacrificial material 214 may be formed on the structure of FIG. 2Abefore any residue (e.g., etch residue) resulting from the dry etchforming features 211 is removed.

In some examples, different portions of the dry removal tool 435 (e.g.,the dry removal tool frame) may be respectively located in differentprocessing chambers, such as chambers 436 and 437 in FIG. 4. Forexample, the dry etch may be performed at one portion of the dry removaltool frame in chamber 436, and sacrificial material 214 may be formed ata different portion of the dry etch tool frame in chamber 437. Thestructure may be moved between the chambers in a vacuum to preventcondensation on features 211 (e.g., in openings 212) and oxidation offeatures 211.

Subsequently, the structure of FIG. 2B may be moved from one processingtool, such as the dry-etch processing tool, to a different processingtool, such as the wet cleaning tool 439 in FIG. 4. For example, thestructure of FIG. 2B may be exposed to a moisture-containing atmosphereas it is moved from one tool to another. However, by closing openings212 and covering features 211, sacrificial material 214 preventscondensation on features 211 in openings 212, and thus the toppling offeatures 211 resulting from the condensation. Sacrificial material 214also protects features 211 from oxidation that can occur as thestructure is being moved through an oxygen containing atmosphere, suchas air. For example, oxidation can consume portions of features 211, andremoval of the resulting oxides may alter the size and/or shape offeatures 211.

The wet cleaning tool 439 may be dedicated to performing wet cleaningthat can remove the residues that may form as a result of the dry etch.In some examples, the composition of sacrificial material 214 may beselected based on the wet clean chemistry to be used for wet cleaning.For instance, the type of sacrificial material 214 to be used to fillopenings 212 may be selected so it can be removed by the wet cleanchemistry to be used for wet cleaning.

As shown in FIG. 2C, sacrificial material 214, as well as residualmaterial from the dry-etch process, is removed from the structure ofFIG. 2B via the wet clean at the wet cleaning tool 439 (e.g., as part ofthe wet cleaning process) to re-expose (e.g., reopen) the openings 212between features 211. In an example, the wet cleaning process may beperformed in a gas-free atmosphere so that the structure of FIG. 2C isnot exposed to a gas.

In some examples the wet cleaning may include an aqueous wet clean thatmay include hydrofluoric acid (HF). In an example, an aqueous wet cleanmay include a standard clean-1 (SC-1) (e.g. for removing organics,particles, and films) that may include deionized (DI) water, aqueousammonium hydroxide, and aqueous hydrogen peroxide. In some instances, astandard clean-2 (SC-2) (e.g., for removing metal ions) that may includedeionized (DI) water, aqueous ammonium hydroxide, and aqueous hydrogenperoxide may be performed after SC-1 as part of the aqueous wet clean.The wet-cleaning process may further include the aqueous wet clean witha DI water rinse, followed by an isopropyl (IPA) rinse, followed bydrying, such as spin drying, to form the structure of FIG. 2C. In otherexamples, wet cleaning process and the removal of the sacrificial 214may be integrated, and the wet cleaning process may remove residue fromthe dry etch.

Subsequently, as shown in FIG. 2D, a sacrificial material 220, such as avolatile solid material, is formed on (e.g., is used to coat) thestructure of FIG. 2C at the wet cleaning tool 439 to close openings 212(e.g., without exposing the structure to a gas). For example,sacrificial material 220 may be spin coated onto the structure of FIG.2C. In some examples, sacrificial material 220 closes openings 212 bycompletely filling openings 212. In some examples, sacrificial material220 can completely fill openings 212 such that an upper surface ofsacrificial material 214 may be coplanar (e.g., flush) with the uppersurfaces 216 of features 211. Additionally, as shown in FIG. 2D,sacrificial material 214 can overfill openings 212 and extend over(e.g., cover) upper surfaces 216 of features 211. In some examples,sacrificial material 220 may completely displace any liquid from the wetcleaning process. Non-limiting examples of suitable volatile materialsinclude camphor, ammonium acetate, camphene, naphthalene, and phenol,succinonitrile, trioxane, acetamide among others. In some examples,sacrificial material 220 may have a melting temperature between 25Celsius and 80 Celsius. For example, such sacrificial materials mayinclude camphene (e.g., melting temperature 52 Celsius), phenol (e.g.,melting temperature 40 Celsius), succinonitrile (e.g., meltingtemperature 54 Celsius), trioxane (e.g., melting temperature 64Celsius), naphthalene (e.g., melting temperature 80 Celsius), andacetamide (e.g., melting temperature 81 Celsius).

In some examples, the volatile material may be melted to create aliquid. The liquid can then be applied to the structure of FIG. 2C andallowed to solidify to form the structure of FIG. 2D. For instance, theliquid can be deposited on to the structure of FIG. 2C and into openings212 in FIG. 2C and then solidified to form the structure of FIG. 2D. Forexample, the temperature of the semiconductor 206 may be reduced tobelow the solidification (e.g., freezing) temperature of the liquid tosolidify the liquid. In some examples, the deposited liquid may displaceany liquid from the wet cleaning process.

In other examples, the volatile material may be dissolved in a solventto create a liquid solution. The solution may then be deposited intoopenings 212 in FIG. 2C. The solvent may then be evaporated, leaving thevolatile material in openings 212.

Subsequently, the structure of FIG. 2D is moved from the wet cleaningtool to a different processing tool, such as the deposition tool 441(see FIG. 4). For example, the structure of FIG. 2D may be exposed to amoisture-containing atmosphere as it is moved from the wet cleaning tool439 to the deposition tool 441. However, by closing openings 212 andcovering features 211, sacrificial material 220 prevents condensation onthe features 211 and in openings 212, and thus the toppling of features211 resulting from the condensation. Sacrificial material 220 may alsoprotect features 211 from oxidation that can occur as the structure isbeing moved through an oxygen containing atmosphere.

As shown in FIG. 2E, sacrificial material 220 may be removed at thedeposition tool 441 to re-expose openings 212 between features 211. Forexamples in which sacrificial material 220 is a volatile material,sacrificial material 220 may be removed by sublimation. For instance,the pressure and temperature at the deposition tool may be set such thatsacrificial material 220 sublimates. For example, the pressure may becontrolled by a pressure controller 442 and temperature may becontrolled by a temperature controller 443, as shown in FIG. 4.

In other examples, sacrificial material 220 may be a dielectricmaterial, such as silicon oxide and/or silicon nitride, that is formedon the structure of FIG. 2C via deposition (e.g., by spin coating) toform the structure of FIG. 2D. For instance, sacrificial material 220may be a spin on dielectric (SOD) material. The SOD material may bebaked, but only partially densified, for example. In an alternativeembodiment, the structure of 2D, including the SOD material, may bemoved from the wet cleaning tool 439 to a different processing tool,such as the dedicated removal tool 445 (e.g., dedicated to removing theSOD material) shown in FIG. 4. For example, the structure of FIG. 2D maybe exposed to a moisture-containing atmosphere as it is moved from thewet-cleaning tool 439 to the removal tool 445, while it is protectedfrom the air by the SOD material. The SOD material may be removed at theremoval tool 445 by a dry etch, such as a vapor etch (e.g., usingvaporized HF if the SOD material is an oxide), to re-expose openings212. Subsequently, the structure of FIG. 2E may be placed in a vacuum toreduce the likelihood of (e.g., to prevent) condensation and oxidation.

In some examples, as shown in FIG. 2F, a material 222 may be formed inthe openings 212 in the structure of FIG. 2E at the deposition tool 441.For example, material 222 may be formed in a gaseous phase or a plasmaphase, such as by PVD, CVD, ALD, among others. For example, material 222might be an epitaxial silicon material or a dielectric material, such assilicon oxide or silicon nitride. In some examples, material 222 mayoverfill openings 212 and extend over the upper surfaces 216 of features211. Subsequently, a portion of material 222 may be removed, such as bychemical mechanical planarization (CMP) so that upper surfaces 224 ofmaterial 222 are coplanar with upper surfaces 216, as shown in FIG. 2F.

In some examples, portions below surface 208 may be isolation regions.In examples in which features 211 may be comprised entirely ofsemiconductor 206, rather than a subsequently deposited material aspreviously described in conjunction with FIG. 2A, and the regionsbetween features 211 containing solid material 222 may be isolationregions.

In some examples, openings 212 in the structure of FIG. 2A and in thestructure of FIG. 2C may be closed without completely filling openings212 with a sacrificial material, such as sacrificial material 214 inFIG. 2B or sacrificial material 220 in FIG. 2D. As shown in FIG. 3, asacrificial material 330 may be formed on a structure, such as thestructure of FIG. 2A or on the structure of FIG. 2C, to form thestructure in FIG. 3. Sacrificial material 330 is formed in openings 312between features 311 so that sacrificial material 330 closes theopenings 312 adjacent to a top of the openings 312 without completelyfilling the openings 312. Sacrificial material 330 pinches off adjacentto the top of the openings before the openings are completely filled,leaving voids 332 between features 311. For example, sacrificialmaterial 330 lines openings 312 and closes off openings 312 adjacent tothe tops of openings 312 to create voids 332. For instance, thesacrificial material 330 is coupled between adjacent features 311 byspanning upper portions of the openings between the adjacent features311.

In some examples, sacrificial material 330 may be sacrificial material214, and the structure of FIG. 3 may be formed at the dry removal tool435, as described previously. Subsequently, the structure of FIG. 3 maybe moved from the dry removal tool (e.g., through moist air) to the wetcleaning tool 439. Sacrificial material 330 is then removed at the wetcleaning tool 435, as described previously, to from the structure ofFIG. 2C.

In some examples, sacrificial material 330 may be sacrificial material220, such as a volatile material or an SOD material, and the structureof FIG. 3 may be formed at the wet cleaning tool 439, as describedpreviously. For example, in the case of sacrificial material 330 being avolatile material, the structure of FIG. 3 may be moved from the wetcleaning tool (e.g., through a moist atmosphere) to the deposition tool441 at which sacrificial solid 330 may be removed by sublimation to formthe structure of FIG. 2E, as described previously. In some examples, thestructure of FIG. 3 may be formed by applying the volatile solid as aliquified solid and allowing the liquified solid to solidify.Alternatively, the structure of FIG. 3 may be formed by depositing thevolatile solid from a solution by evaporating the solvent. In otherexamples, sacrificial material 330 may be deposited to partially fillopenings 312 such that sacrificial material 330 is formed on features311 within openings 312, as shown in FIG. 3, thus lining openings 312,but without pinching off.

In examples in which sacrificial material 330 is an SOD, the structuremay be moved from the wet cleaning tool 439 (e.g., through moistatmosphere) to the removal tool 445, at which sacrificial material 330may be removed by a dry etch to form the structure of FIG. 2E, asdescribed previously.

FIG. 5 is a block diagram of an apparatus, such as a memory device 550.For example, memory device 550 may be a volatile memory device, such asa DRAM, a non-volatile memory device, such as NAND flash or NOR flash,among others. For example, memory device 550 may be formed, at least inpart, using the processing previously described, such as in conjunctionwith FIGS. 2A-2F and FIG. 3.

Memory device 550 includes a controller 552, such as an applicationspecific integrated circuit (ASIC), coupled to a memory array 554, suchas a DRAM array, a NAND array, a NOR array, among others. For example,memory array 454 might be formed, at least in part, according to theprocessing described previously.

The controller 552 can control the operations on the memory device 550,and of the memory array 554, including data sensing (e.g., reading) anddata programming (e.g., writing), for example. Memory device 550 may becoupled to a host device (not shown in FIG. 5).

Embodiments of the disclosure use sacrificial materials to closeopenings in structures (e.g., to be used in semiconductor devices, suchas integrated circuits, memory devices, MEMS, and the like), such asbetween features in the structures. The sacrificial materials preventcondensate from forming in the openings as the structures are movedthrough moist atmospheres between tools, thereby preventing the featuresfrom toppling.

Although specific examples have been illustrated and described herein,those of ordinary skill in the art will appreciate that an arrangementcalculated to achieve the same results may be substituted for thespecific embodiments shown. This disclosure is intended to coveradaptations or variations of one or more embodiments of the presentdisclosure. It is to be understood that the above description has beenmade in an illustrative fashion, and not a restrictive one. The scope ofone or more examples of the present disclosure should be determined withreference to the appended claims, along with the full range ofequivalents to which such claims are entitled.

What is claimed is:
 1. A method of forming a semiconductor device,comprising: forming a plurality of features in a structure using a dryremoval tool; closing openings between the features with a sacrificialmaterial at the dry removal tool; moving the structure to a wet cleaningtool; and removing the sacrificial material and residue left fromforming the plurality of features using the wet cleaning tool.
 2. Themethod of claim 1, wherein the sacrificial material is a dielectricmaterial or a conductive material.
 3. The method of claim 1, wherein thesacrificial material is soluble in a solvent.
 4. The method of claim 1,wherein different portions of the dry removal tool are respectivelylocated in different processing chambers, and the method furthercomprises: forming the plurality of features in one of the chambers; andclosing the openings in the other one of the chambers.
 5. A method offorming a semiconductor device, comprising: forming a plurality offeatures in a structure using a dry removal tool; closing openingsbetween the features with a first sacrificial material at the dryremoval tool; moving the structure to a wet cleaning tool; removing thefirst sacrificial material using the wet cleaning tool; after removingthe first sacrificial material, closing the openings with a secondsacrificial material at the wet cleaning tool; moving the structure to adeposition tool; and removing second solid sacrificial material at thedeposition tool by sublimation.
 6. The method of claim 5, furthercomprising after removing the second sacrificial material, using thedeposition tool to form an additional material on the structure.
 7. Themethod of claim 5, wherein removing second solid sacrificial material bysublimation comprises setting a pressure and temperature at thedeposition tool so the second solid sacrificial material sublimates.